2. Be different. Everyone expects a Mekhet to be sneaky and perceptive, a Gangrel to be wild and unkempt, etc. Do something different--break the mold. Be a Nosferatu socialite, an awkward Ventrue, a hideous Daeva. Be a hardened war vet who hung up the rifle to pursue knitting little hats for kittens. Be an underwear model with crippling anxiety and an incurable stutter. Instead of picking what intuitively fits your character, throw in a wrinkle that seems to completely contradict your concept. This is a great way to make characters more three-dimensional. In the same vein...
3. Be suboptimal. Constantly thinking about, and trying to justify, a bigger dice pool is a great way to make a boring character. Sure, one way for a grizzled old PI to react to stress is to spend more time at the firing range and boost his Firearms Skill. But another way might be to grab a dot of Animal Ken and adopt a puppy. One of these things results in an additional die to roll next time your character is in a firefight; the other results in an entirely new and humanizing dimension being added to your character concept. (And maybe next time danger comes calling, that Pit Bull won't seem so useless after all...)
4. Be vulnerable. Allow your character to be affected by things. Allow them to care, to feel, to get attached. Most importantly, allow them to be hurt. If your character is the stoic type, fine--make it a point to telegraph his emotions in small but obvious ways, or let other characters see him break down in tears when he thinks no one's looking.
5. Be impulsive. Few things are more boring than a bunch of PCs sitting in a room debating options for hours on end as they try to come up with the perfect solution to a problem. Stop trying to account for every possible permutation and just go do something. Anything. It doesn't have to be smart. Dumb ideas make fantastic roleplaying opportunities (and hilarious stories to tell and retell later). And literally anything is better than talking in circles until everyone gets bored and falls asleep.
6. Be supportive. Try this, as an experiment: next time a story arc comes, don't think about how your PC can get into the spotlight. Instead, think about which of the other PCs is best suited for the starring role--and then push that character as hard as you can to center stage. Alternatively, consider allowing other PCs to share the stage even if the story arc is meant for you. Put your PC into another's debt, give them a chance to shine--and when they call in that debt later, it'll be your turn. This kind of generosity will make people enjoy interacting with you both IC and OOC--and supporting roles are often more rewarding and memorable than starring ones anyway.